/Engine/Source/Runtime/Engine/Classes/GameFramework/CharacterMovementComponent.h
Calculate slide vector along a surface. Has special treatment when falling, to avoid boosting up slopes (callingHandleSlopeBoosting()in this case).
New deflected vector of movement.
virtual FVector ComputeSlideVector ( const FVector & Delta, const float Time, const FVector & Normal, const [FHitResult](API\Runtime\Engine\Engine\FHitResult) & Hit ) const